License Movement

Tracking latitudinal movement of GARFO licenses

By rounding latitude to 1/10 of a degree, we can calculate the center of gravity/occurrence of a license type. To do this, we weight the average latitude by the total number of a particular license type associated with that latitude over time.

Black sea bass

Black sea bass is used as an example, as there are only two license types and a distinguishable trend of northward (poleward) latitudinal movement.

Bluefish

Multispecies

Squid, mackerel, and butterfish

Skate

Scup

Geographic spread

There’s no clear trend at this scale of license distribution changing. In the center of gravity analysis, there is a strong southward trend of multispecies groundfish licenses. We will run a GINI analysis later but first will plot the raw latitude data as boxplot to understand the spread of these license categories. It might be useful to compare the groundfish landings trends to the license trend so see if there are correlative shifts.

There is a very subtle trend of the median moving southwards, likely being pulled towards all the southern outliers, which seem to outnumber northward outliers.